Within this box fits a Shelly 1 or 1PM and two WAGO 221 connection clamps for easy cable connection. Cables are secured by two printed cable clamps.
I used threaded inserts from ruthex in size M3 for the screws.
Update 12/07/2022: added another Base option without WAGO terminals. Some people might prefer that.
Update 12/08/2022: Looks like the dimensions from the Shelly website were actually smaller than the device itself. I corrected the dimensions in the design and uploaded the new versions.
The author hasn't provided the model origin yet.